Miniature silicon condenser microphone

ABSTRACT

A silicon condenser microphone package includes a transducer unit, a substrate, and a cover. The substrate includes an upper surface transducer unit is attached to the upper surface of the substrate and overlaps at least a portion of the recess wherein a back volume of the transducer unit is formed between the transducer unit and the substrate. The cover is placed over the transducer unit and either the cover or the substrate includes an aperture.

RELATED APPLICATION

This application is a division of U.S. application Ser. No. 09/886,854,filed Jun. 21, 2001, now U.S. Pat. No. 7,166,910, which claims thebenefit of Provisional Patent Application Ser. No. 60/253,543 filed Nov.28, 2000.

TECHNICAL FIELD

The present invention relates generally to a housing for a transducer.More particularly, this invention relates to a miniature siliconcondenser microphone comprising a housing for shielding a transducerproduced on the surface of a silicon die. The silicon die must bepackaged to produce a functional microphone of this type.

BACKGROUND OF THE INVENTION

There have been a number of disclosures related to building microphoneelements on the surface of a silicon die. Certain of these disclosureshave come in connection with the hearing aid field for the purpose ofreducing the size of the hearing aid unit. While these disclosures havereduced the size of the hearing aid, they have not disclosed how toprotect the transducer from outside interferences. For instance,transducers of this type are fragile and susceptible to physical damage.Furthermore, they must be protected from light and electromagneticinterferences. Moreover, they require an acoustic pressure reference tofunction properly. For these reasons, the silicon die must be shielded.

Some shielding practices have been used to house these devices. Forinstance, insulated metal cans or discs have been provided.Additionally, DIPS and small outline integrated circuit (SOIC) packageshave been utilized. However, the drawbacks associated with manufacturingthese housings, such as lead time, cost, and tooling, make these optionsundesirable.

SUMMARY OF THE INVENTION

The present invention is directed to a silicon condenser microphonepackage which allows acoustic energy to contact a transducer whichprovides the necessary pressure reference while at the same timeprotects the transducer from light, electromagnetic interference, andphysical damage. A silicon condenser microphone package comprises atransducer, a substrate, and a cover. The substrate has an upper surfacewith a recess formed therein. The transducer is attached to the uppersurface of the substrate and overlaps at least a portion of the recessso that a back volume of the transducer is formed between the transducerand the substrate. The cover is placed over the transducer and includesan aperture adapted for allowing sound waves to reach the siliconcondenser transducer.

Other features and advantages of the invention will be apparent from thefollowing specification taken in conjunction with the followingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a first embodiment of a siliconcondenser microphone of the present invention;

FIG. 2 is a cross-sectional view of a second embodiment of a siliconcondenser microphone of the present invention;

FIG. 3 is a cross-sectional view of a third embodiment of a siliconcondenser microphone of the present invention;

FIG. 4 is a cross-sectional view of the third embodiment of the presentinvention affixed to an end user circuit board;

FIG. 5 is a cross-sectional view of the third embodiment of the presentinvention affixed to an end user circuit board in an alternate fashion;

FIG. 6 is a plan view of a substrate to which a silicon condensermicrophone is fixed;

FIG. 7 is a longitudinal cross-sectional view of a microphone package ofthe present invention;

FIG. 8 is a lateral cross-sectional view of a microphone package of thepresent invention;

FIG. 9 is a longitudinal cross-sectional view of a microphone package ofthe present invention;

FIG. 10 is a lateral cross-sectional view of a microphone package of thepresent invention;

FIG. 11 is a cross-sectional view of a top portion for a microphonepackage of the present invention;

FIG. 12 is a cross-sectional view of a top portion for a microphonepackage of the present invention;

FIG. 13 is a cross-sectional view of a top portion for a microphonepackage of the present invention;

FIG. 14 a is a cross-sectional view of a laminated bottom portion of ahousing for a microphone package of the present invention;

FIG. 14 b is a plan view of a layer of the laminated bottom portion ofFIG. 14 a;

FIG. 14 c is a plan view of a layer of the laminated bottom portion ofFIG. 14 a;

FIG. 14 d is a plan view of a layer of the laminated bottom portion ofFIG. 14 a;

FIG. 15 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 16 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 17 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 18 is a cross-sectional view of a bottom portion for a microphonepackage of the present invention;

FIG. 19 is a plan view of a side portion for a microphone package of thepresent invention;

FIG. 20 is a cross-sectional package view of a side portion for amicrophone package of the present invention;

FIG. 21 is a cross-sectional view of a side portion for a microphonepackage of the present invention;

FIG. 22 is a cross-sectional view of a side portion for a microphonepackage of the present invention;

FIG. 23 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 24 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 25 is across-sectional view of a microphone package of the presentinvention;

FIG. 26 is a cross-sectional view of a microphone package of the presentinvention;

FIG. 27 is a cross-sectional view of a microphone package of the presentinvention with a retaining ring;

FIG. 28 is a cross-sectional view of a microphone package of the presentinvention with a retaining wing; and

FIG. 29 is a cross-sectional view of a microphone package of the presentinvention with a retaining ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While this invention is susceptible of embodiments in many differentforms, there is shown in the drawings and will herein be described indetail preferred embodiments of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiments illustrated.

The present invention is directed to microphone packages. The benefitsof the microphone packages disclosed herein over microphone packagingutilizing plastic body/lead frames include the ability to processpackages in panel form allowing more units to be formed per operationand at much lower cost. The typical lead frame for a similarlyfunctioning package would contain between 40 and 100 devices connectedtogether. The present disclosure would have approximately 14,000 devicesconnected together (as a panel). Also, the embodiments disclosed hereinrequire minimal “hard-tooling.” This allows the process to adjust tocustom layout requirements without having to redesign mold, lead frame,and trim/form tooling.

Moreover, these embodiments have a better match of thermal coefficientsof expansion with the end user's PCB since this part would typically bemounted on FR-4 which is the same material used by end users. Thepresent designs may also eliminate the need for wire bonding that isrequired in plastic body/lead frame packages. The foot print istypically smaller than that would be required for a plastic body/leadframe design since the leads are formed by plating a through-hole in acircuit board of which one half will eventually form the pathway to thesolder pad. In a typical plastic body/lead frame design, a gull in whichthe leads are disposed, widen the overall foot print.

Now, referring to FIGS. 1-3, three embodiments of a silicon condensermicrophone package 10 are illustrated. The silicon microphone package 10generally comprises a transducer 12, e.g. a silicon condenser microphoneas disclosed in U.S. Pat. No. 5,870,482 which is hereby incorporated byreference, a substrate 14, an amplifier 16, a back volume or air cavity18 which provides a pressure reference for the transducer 12, and acover 20. The substrate 14 is typically formed of FR-4 material whichmay be processed in circuit board panel form, thus taking advantage ofeconomies of scale in manufacturing. FIG. 6 is a plan view of thesubstrate 14 showing the back volume 18 surrounded a plurality ofterminal pads.

The back volume 18 may be formed by a number of methods, includingcontrolled depth drilling of an upper surface 19 of the substrate 14 toform a recess over which the silicon condenser microphone is mounted(FIG. 1); drilling and routing of several individual sheets of FR-4 andlaminating the individual sheets to form the back volume 18 which may ormay not have internal support posts (FIG. 2); or drilling completelythrough the substrate 14 and providing a sealing ring 22 on the bottomof the device that will seal the back volume 18 during surface mountingto a user's “board” 28 (FIGS. 3-5). In this example, the combination ofthe substrate and the user's board 28 creates the back volume 18. Theback volume 18 is covered by the transducer 12 (MEMS device) which is“bumpbonded” and mounted face down. The boundary is sealed such that theback volume 18 is “air-tight”.

The cover 20 is attached for protection and processibility. The cover 20contains an aperture 24 which may contain a sintered metal insert 26 toprevent water, particles and/or light from entering the package anddamaging the internal components inside; i.e. semiconductor chips. Theaperture 24 is adapted for allowing sound waves to reach the transducer12.

Referring to FIGS. 4 and 5, the final form of the product (shown withoutthe cover 20) is a silicon condenser microphone package 10 which wouldmost likely be attached to a end user's PCB 28 via a solder reflowprocess. FIG. 5 illustrates a method of enlarging the back volume 18 byincluding a chamber 32 within the end user's circuit board 28.

Another embodiment of a silicon condenser microphone package 40 isillustrated in FIGS. 7-10. In this embodiment, a housing 42 is formedfrom layers of materials, such as those used in providing circuitboards. Accordingly, the housing 42 generally comprises alternatinglayers of conductive and non-conductive materials 44, 46. Thenon-conductive layers 46 are typically FR-4 board. The conductive layers44 are typically copper.

In the embodiment illustrated, the housing 42 includes a top portion 48and a bottom portion 50 spaced by a side portion 52. The housing 42further includes an aperture or acoustic port 54 for receiving anacoustic signal and an inner chamber 56 which is adapted for housing atransducer unit 58, typically a silicon die microphone or a ball gridarray package (BGA). The top, bottom, and side portions 48, 50, 52 areelectrically connected, for example with a conductive adhesive 60. Eachportion may comprise alternating conductive and non-conductive layers of44, 46.

The chamber 56 includes an inner lining 61. The inner lining 61 isprimarily formed by conductive material. It should be understood thatthe inner lining may include portions of non-conductive material, as theconductive material may not fully cover the non-conductive material. Theinner lining 61 protects the transducer 58 against electromagneticinterference and the like, much like a faraday cage.

In the various embodiments illustrated in FIGS. 7-10 and 23-26, theportions of the housing 42 that include the aperture or acoustic port 54further include a layer of material that forms an environmental barrier62 over or within the aperture 54. This environmental barrier 62 istypically a polymeric material formed to a film, such as apolytetrafluoroethylene (PTFE) or a sintered metal. The environmentalbarrier 62 is supplied for protecting the chamber 56 of the housing 42,consequently, the transducer unit 58 within the housing 42, fromenvironmental elements such as sunlight, moisture, oil, dirt, and/ordust.

The environmental barrier layer 62 is generally sealed between twolayers of conductive material 44. When the environmental barrier layer62 is sandwiched between two layers of conductive material 44, it mayact as a capacitor (with electrodes defined by the metal) that can beused to filter input and output signals or the input power. Theenvironmental barrier layer 62 may further serve as a dielectricprotective layer when in contact with the conductive layers 44 in theevent that the conductive layers also contain thin film passive devicessuch as resistors and capacitors.

In addition to protecting the chamber 56 from environmental elements,the barrier layer 62 allows subsequent wet processing, board washing ofthe external portions of the housing 42, and electrical connection toground from the walls via thru hole plating. The environmental barrierlayer 62 also allows the order of manufacturing steps in the fabricationof the printed circuit board-based package to be modified. Thisadvantage can be used to accommodate different termination styles. Forexample, a double sided package can be fabricated having a pair ofapertures 54 (see FIG. 25), both including an environmental barrierlayer 62. The package would look and act the same whether it is mountedface up or face down, or the package could be mounted to providedirectional microphone characteristics.

Referring to FIGS. 7, 8, and 11-13, the transducer unit 58 is generallynot mounted to the top portion 48 of the housing. This definition isindependent of the final mounting orientation to an end user's circuitboard. It is possible for the top portion 48 to be mounted face downdepending on the orientation of the transducer 58 as well as the choicefor the bottom portion 50. The conductive layers 44 of the top portion48 may be patterned to form circuitry, ground planes, solder pads,ground pads, and plated through hole pads. Referring to FIGS. 11-13,there may be additional alternating conductive layers 44, non-conductivelayers 46, and environmental protective membranes 62 as the packagerequires. Alternatively, some layers may be deliberately excluded aswell. The first non-conductive layer 46 may be patterned so as toselectively expose certain features on the first conductive layer 44.

FIG. 11 illustrates an alternative top portion 48 for a microphonepackage. In this embodiment, a connection between the layers can beformed to provide a conduit to ground. The top portion of FIG. 11includes ground planes and/or pattern circuitry 64 and the environmentalbarrier 62. The ground planes and or pattern circuitry 64 are connectedby pins 65.

FIG. 12 illustrates another embodiment of a top portion 48. In additionto the connection between layers, ground planes/pattern circuitry 64,and the environmental barrier 62, this embodiment includes conductivebumps 66 (e.g. Pb/Sn or Ni/Au) patterned on the bottom side to allowsecondary electrical contact to the transducer 58. Here, conductivecircuitry would be patterned such that electrical connection between thebumps 66 and a plated through hole termination is made.

FIG. 13 illustrates yet another embodiment of the top portion 48. Inthis embodiment, the top portion 48 does not include an aperture oracoustic port 54.

Referring to FIGS. 7, 8 and 14-18, the bottom portion 50 is thecomponent of the package to which the transducer 58 is primarilymounted. This definition is independent of the final mountingorientation to the end user's circuit board. It is possible for thebottom portion 50 to be mounted facing upwardly depending on themounting orientation of the transducer 58 as well as the choice for thetop portion 48 construction. Like the top portion 48, the conductivelayers 44 of the bottom portion 50 may be patterned to form circuitry,ground planes, solder pads, ground pads and plated through hole pads. Asshown in FIGS. 14-18, there may be additional alternating conductivelayers 44, non-conductive layers 46, and environmental protectivemembranes 62 as the package requires. Alternatively, some layers may bedeliberately excluded as well. The first non-conductive layer 46 may bepatterned so as to selectively expose certain features on the firstconductive layer 44.

Referring to FIGS. 14 a through 14 d, the bottom portion 50 comprises alaminated, multi-layered board including layers of conductive material44 deposited on layers of non-conductive material 46. Referring to FIG.14 b, the first layer of conductive material is used to attach wirebonds or flip chip bonds. This layer includes etched portions to definelead pads, bond pads, and ground pads. The pads would have holes drilledthrough them to allow the formation of plated through-holes.

As shown in FIG. 14 c, a dry film 68 of non-conductive material coversthe conductive material. This illustration shows the exposed bondingpads as well as an exposed ground pad. The exposed ground pad would comein electrical contact with the conductive epoxy and form the connectionto ground of the side portion 52 and the base portion 50.

Referring to FIG. 14 d, ground layers can be embedded within the baseportion 50. The hatched area represents a typical ground plane 64. Theground planes do not overlap the power or output pads, but will overlapthe transducer 58.

Referring to FIG. 15, an embodiment of the bottom portion 50 isillustrated. The bottom portion 50 of this embodiment includes a soldermask layer 68 and alternating layers of conductive and non-conductivematerial 44, 46. The bottom portion further comprises solder pads 70 forelectrical connection to an end user's board.

FIGS. 16 and 17 illustrate embodiments of the bottom portion 50 withenlarged back volumes 18. These embodiments illustrate formation of theback volume 18 using the conductive/non-conductive layering.

FIG. 18 shows yet another embodiment of the bottom portion 50. In thisembodiment, the back portion 50 includes the acoustic port 54 and theenvironmental barrier 62.

Referring to FIGS. 7-10 and 19-22, the side portion 52 is the componentof the package that joins the bottom portion 50 and the top portion 48.The side portion 51 may include a single layer of a non-conductivematerial 46 sandwiched between two layers of conducive material 44. Theside portion 48 forms the internal height of the chamber 56 that housesthe transducer 58. The side portion 52 is generally formed by one ormore layers of circuit board material, each having a routed window 72(see FIG. 18).

Referring to FIGS. 19-22, the side portion 52 includes inner side wall74. The inner side walls 74 are generally plated with a conductivematerial, typically copper, as shown in FIGS. 20 and 21. The side wall74 are formed by the outer perimeter of me routed window 72 andcoated/metallized with a conductive material.

Alternatively, the side wall 74 may be formed by many alternating layersof non-conductive material 46 and conductive material 44, each having arouted window 72 (see FIG. 19). In this case, the outer perimeter of thewindow 72 may not require coverage with a conductive material becausethe layers of conductive material 44 would provide effective shielding.

FIGS. 23-26 illustrate various embodiments of the microphone package 40.These embodiments utilize top, bottom, and side portions 48, 50, and 52which are described above. It is contemplated that each of the top,bottom, and side portion 48, 50, 52 embodiments described above can beutilized in any combination without departing from the inventiondisclosed and described herein.

In FIG. 23, connection to an end user's board is made through the bottomportion 50. The package mounting orientation is bottom portion 50 downconnection from the transducer 58 to the plated through holes is be madeby wire bonding. The transducer back volume 18 is formed by the backhole (mounted down) of the silicon microphone only. Bond pads, wirebonds and traces to the terminals are not shown. A person of ordinaryskilled in the art of PCB design will understand that the traces resideon the first conductor layer 44. The wire bonds from the transducer 58are be connected to exposed pads. The pads are connected to the solderpads via plated through holes and traces on the surface.

In FIG. 24, connection to the end user's board is also made through thebottom portion 50. Again, the package mounting orientation is bottomportion 50 connection from the transducer 58 to the plated through holesare made by wire bonding. The back volume 18 is formed by a combinationof the back hole of the transducer 58 (mounted down) and the bottomportion 50.

In FIG. 25, connection to the end user's board is also made through thebottom portion 50. Again, the package mounting orientation is bottomportion 50 connection from the transducer 58 to the plated through holesare made by wire bonding. With acoustic ports 54 on both sides of thepackage, there is no back volume, This method is suitable to adirectional microphone.

In FIG. 26, connection to the end user's board is made through the topportion 48 of the bottom portion 50. The package mounting orientation iseither top portion 48 down or bottom portion 50 down. Connection fromthe transducer 58 to the plated through holes is made by flip chippingand trace routing. The back volume 18 is formed by using the air cavitycreated by laminating the bottom portion 50 and the top portion 48together. Some portion of the package fabrication is performed after thetransducer 58 has been attached. In particular, the through holeformation, plating, and solder pad definition would be done after thetransducer 58 is attached. The protective membrane 62 is hydrophobic andprevents corrosive plating chemistry from entering the chamber 56.

Referring to FIGS. 27-29, the portion to which the transducer unit 58 ismounted may include a retaining ring 84. The retaining ring 84 preventswicking of an epoxy 86 into the transducer 58 and from flowing into theacoustic port or aperture 54. Accordingly, the shape of the retainingring 84 will typically match the shape of the transducer 58 foot print.The retaining ring 84 comprises a conductive material (e.g., 3 mil.thick copper) imaged on a non-conductive layer material.

Referring to FIG. 27, the retaining ring 84 is imaged onto anon-conductive layer. An epoxy is applied outside the perimeter of theretaining ring 84, and the transducer 58 is added so that it overlapsthe epoxy 86 and the retaining ring 84. This reduces epoxy 86 wicking upthe sides of the transducer's 58 etched port (in the case of a silicondie microphone).

Alternatively, referring to FIG. 28, the retaining ring 84 can belocated so that the transducer 58 does not contact the retaining ring84. In this embodiment, the retaining ring 84 is slightly smaller thanthe foot print of the transducer 58 so that the epoxy 86 has arestricted path and is, thus, less likely to wick. In FIG. 29, theretaining ring 84 is fabricated so that it contacts the etched port ofthe transducer 58.

The following tables provide an illustrative example of a typicalcircuit board processing technique for fabrication of the housing ofthis embodiment.

TABLE 1 Materials Ma- terial Type Component Note 1 0.5/0.5 oz. DSTBottom Portion (Conductive Cu 5 core FR-4 Layers 1 and 2; Non-Conductive Layer 1) 2 0.5/0.5 oz. DST Bottom Portion (Conductive Cu 5core FR-4 Layers 3 and 4; Non- Conductive Layer 2) 3 106 pre-preg ForLaminating Material 1 and Material 2 4 0.5/0.5 oz. DST Side PortionMetallized Cu 40 Core FR-4 Afterward 5 Bare/0.5 oz. Cu 2 Top Portion(Each Piece core FR-4 (2 Includes 1 Conductive and 1 pieces)Non-Conductive Layer) 6 Expanded PTFE Environmental Barrier

2: Processing of Materials (Base Portion Material 1) Step TypeDescription Note 1 Dry Film Conductive Layers 2 Expose Mask Material 1(Lower Forms Ground Conductive Layer). Plane on Lower Conductive Layer 3Develop 4 Etch Cu No Etching on Upper Conductive Layer 5 Strip Dry Film

TABLE 3 Processing of Materials (Bottom Portion Material 2) Step TypeDescription Note 1 Dry Film Conductive Layers 2 Expose Mask Material 2(Upper Forms Ground Conductive Layer) Plane on Upper Conductive Layer 3Develop 4 Etch Cu No Etching on Lower Conductive Layer 5 Strip Dry Film

TABLE 4 Processing of Materials 1, 2, and 3 (Form Bottom Portion) StepType Description Note 1 Laminate Materials 1 and 2 Laminated UsingMaterial 3 2 Drill Thru Holes Drill Bit = 0.025 in. 3 Direct Plates ThruHoles Metallization/Flash Copper 4 Dry Film (L1 and L4) 5 Expose MaskLaminated Forms Traces and Materials 1 and 2 Solder Pads (Upper andLower Conductive Layers) 6 Develop 7 Electrolytic Cu 1.0 mil 8Electrolytic Sn As Required 9 Strip Dry Film 10 Etch Cu 11 Etch Sn 12Insert Finishing NG Option (See NG Option for Proof Option Here TableBelow) of Principle 13 Dry Film (cover 2.5 mil Minimum Thickness lay) onUpper on Upper Conductive Conductive Layer Layer Only 14 Expose MaskLaminated This mask defines an Materials 1 and 2 area on the upper(upper and lower) conductive layer that will receive a dry film soldermask (cover lay). The bottom layer will not have dry film applied to it.The plated through holes will be bridged over by the coating on the top.15 Develop 16 Cure Full Cure 17 Route Panels Route Bit = As Forms 4″ ×4″ pieces. Required Conforms to finished dims

Table 5 describes the formation of the side portion 52. This processinvolves routing a matrix of openings in FR-4 board. However, punchingis thought to be the cost effective method for manufacturing. Thepunching may done by punching through the entire core, or,alternatively, punching several layers of no-flow pre-preg and thin corec-stage which are then laminated to form the wall of proper thickness.

After routing the matrix, the board will have to be electroless or DMplated. Finally, the boards will have to be routed to match the bottomportion. This step can be done first or last. It may make the piece moreworkable to perform the final routing as a first step.

TABLE 5 Processing of Material 4 (Side Portion) Step Type DescriptionNote 1 Route./Punch Route Bit = 0.031 in. Forms Side Portion Matric ofOpenings 2 Direct 0.25 mil minimum Forms Sidewalls Metallization/ onSide Portion Flash Cu 3 Route Panels

Table 6 describes the processing of the top portion. The formation ofthe top portion 48 involves imaging a dry film cover layer or liquidsolder mask on the bottom (i.e. conductive layer forming the innerlayer. The exposed layer of the top portion 48 will not have a coppercoating. It can be processed this way through etching or purchased thisway as a one sided laminate.

A matrix of holes is drilled into the lid board. Drilling may occurafter the imaging step. If so, then a suitable solder mask must bechosen that can survive the drilling process.

TABLE 6 Processing of Top Portion Step Type Description Note 1 Dry FilmConductive Layer 2 Expose Mask Bare Layer Form Conduction Ring 3 Develop4 Cure 5 Drill Matrix Drill Bit = 0.025 in. Acoustic Ports of Holes 6Laminate PTFE (Environmental Barrier) Forms Top Between 2 Pieces ofMaterial 5 Portion

TABLE 7 Processing of Laminated Materials 1 and 2 with Material 4 StepType Description Note 1 Screen Conductive Adhesive on Material 4 2Laminate Bottom Portion with Side Forms Bottom Portion Portion with SidePortion (spacer) 3 Add Transducer Silicon Die Microphone Assembly andIntegrated Circuit

TABLE 8 Processing of Laminated Materials 1, 2, and 4 with Material 5Step Type Description Note 1 Screen Conductive Adhesive on Top Portion 2Laminate Bottom Portion and Side Forms Housing Portion with Top_Portion3 Dice

TABLE 9 Finishing Option NG (Nickel/Gold) Step Type Description Note 1Immersion Ni (40-50, μ-in) 2 Immersion Au (25-30, μ-in)

TABLE 10 Finishing Option NGT (Nickel/Gold/Tin) Step Type 1 Mask L2(using thick dry film or high tack dicing tape) 2 Immersion Ni (40-50,μ-in) 3 Immersion Au (25-30, μ-in) 4 Remove Mask on L2 5 Mask L1 (usingthick dry film or high tack dicing tape) bridge over cavity created bywall 6 Immersion Sn (100-250, μ-in) 7 Remove Mask on L1

TABLE 11 Finishing Option ST (Silver/Tin) Step Type 1 Mask L2 (usingthick dry film or high tack dicing tape) 2 Immersion Ag (40-50 μ-in) 3Remove Mask on L2 4 Mask L1 (using thick dry film or high tack dicingtape) bridge over cavity created by wall 5 Immersion Sri (100-250 μ-in)6 Remove Mask on L1

While specific embodiments have been illustrated and described, numerousmodifications come to mind without significantly departing from thespirit of the invention, and the scope of protection is only limited bythe scope of the accompanying claims.

1. A surface mountable package for containing a transducer, thetransducer being responsive to sound pressure levels of an acousticsignal to provide an electrical output representative of the acousticsignals, the surface mountable package comprising: at least a firstmember and a second member and a chamber being defined by the firstmember and the second member, the transducer being attached to a surfaceformed on one of the first member or the second member and thetransducer residing within the chamber; the surface being formed with atleast one patterned conductive layer, the patterned conductive layerbeing electrically coupled to the transducer; an outside surface of thesurface mountable package comprising a plurality of terminal padselectrically coupled to the patterned conductive layer; a volume beingdefined by the transducer and one of the first member or the secondmember, the volume being acoustically coupled to the transducer; and oneof the first member or the second member being formed to include anaperture, the aperture configured to permit the passage of an acousticsignal to the transducer.
 2. The surface mountable package of claim 1,wherein the first member comprises a substrate and the second membercomprises a cover coupled to the substrate to define the chamber.
 3. Thesurface mountable package of claim 1, the volume includine a recessformed in the surface.
 4. The surface mountable package of claim 1, thevolume including a hole through one of the first member or the secondmember containing the surface.
 5. The surface mountable package of claim1, the surface mountable package being secured to a substrate of adevice, the chamber in communication with a cavity formed in the devicesubstrate.
 6. The surface mountable package of claim 1, the aperturebeing acoustically coupled to a first side of the transducer and thevolume being acoustically coupled to a second side of the transducer. 7.The surface mountable package of claim 1, the aperture being formed inthe respective one of the first member and the second member, thesurface being formed on the respective one of the first member and thesecond member and the transducer being attached to the surfacecompletely covering the aperture.
 8. The surface mountable package ofclaim 1, the aperture being formed in the respective one of the firstmember and the second member, the surface being formed on the respectiveone of the first member and the second member and the transducer beingattached to the surface adjacent to the aperture.
 9. The surfacemountable package of claim 1, the aperture being formed in therespective one of the first member and the second member, the surfacebeing formed on the respective other one of the first member and thesecond member and the aperture is acoustically coupled by the chamber tothe transducer.
 10. The surface mountable package of claim 1, theaperture is formed in the respective one of the first member and thesecond member, the surface is formed on the respective one of the firstmember and the second member and the transducer is attached to thesurface leaving the aperture uncovered by the transducer, wherein theaperture is coupled to the transducer via the chamber.
 11. The surfacemountable package of claim 1, the aperture is formed in each of thefirst member and the second member.
 12. The surface mountable package ofclaim 1, the aperture is formed in the second member, the surface isformed on the first member and the aperture is coupled to the transducervia the chamber; and the volume includes a recess formed in the firstmember.
 13. The surface mountable package of claim 1, the aperture isformed in the respective one of the first member and the second member,the surface is formed on the respective one of the first member and thesecond member and the transducer is attached to the surface covering theaperture and a sealing ring is disposed about and surrounding theaperture, the sealing ring providing a seal between the transducer andthe surface.
 14. The surface mountable package of claim 1, the surfacemountable package being secured to a surface of a device, a sealing ringdisposed about and surrounding the aperture on an outside surface of thesurface mountable package, the sealing ring providing a seal between thesurface mountable package and the surface of the device.
 15. The surfacemountable package of claim 1, the patterned conductive layer comprisinga plurality of terminal pads, the terminal pads providing an electricalconnection between the transducer within the volume and an exterior ofthe surface mountable package.
 16. The surface mountable package ofclaim 1, a metalized region being formed on an exterior surface of thesurface mountable package, the metalized region being electricallycoupled to the patterned conductive layer.
 17. The surface mountablepackage of claim 1, one or both of the first member and the secondmember including a shield against electromagnetic interference.
 18. Thesurface mountable package of claim 1, the first member including a firstconductive portion, the second member including a second conductiveportion, an electromagnetic interference shield being formed by thecoupling of the first conductive portion and the second conductiveportion.
 19. The surface mountable package of claim 18, the firstconductive portion comprising a conductive layer formed in the firstmember and the second conductive portion comprising a conductive layerformed in the second member.
 20. The surface mountable package of claim1, the first member comprising a printed circuit board.
 21. The surfacemountable package of claim 1, a third member being disposed between thefirst member and the second, the first member, the second member and thethird member defining the chamber.
 22. The surface mountable package ofclaim 1, a barrier being disposed within the aperture.
 23. The surfacemountable package of claim 22, wherein the barrier has acousticproperties.
 24. The surface mountable package of claim 23, wherein thebarrier forms an environmental protective barrier.
 25. The surfacemountable package of claim 1, the aperture being formed in therespective one of the first member and the second member, the surfacebeing formed on the respective other one of the first member and thesecond member, the aperture being coupled to the transducer via thechamber and a passage being formed in the respective other one of thefirst member and the second member, the passage being coupled to thetransducer.
 26. The surface mountable package of claim 25, wherein thepassage comprises a portion of an acoustic port.
 27. The surfacemountable package of claim 25, wherein a barrier is disposed within thepassage.
 28. The surface mountable package of claim 1, wherein thevolume includes a portion of the chamber.
 29. The surface mountablepackage of claim 1, wherein the acoustic signal is coupled to thetransducer via the chamber.